Mothers can spread yawns to their yet-to-be-born offspring during pregnancy, researchers report May 5 in Current Biology the first empirical evidence that behavioral contagion, long thought to be a social phenomenon of postnatal life, may have roots in the womb.
Yawning is contagious in many social species, including humans, dogs, lions, and parakeets. Although the behavior is generally thought to increase blood flow to the brain for cooling and alertness a theory known as the thermoregulatory hypothesis yawning may also help synchronize group behavior and function as a primitive form of empathy.
Brain-imaging studies have linked contagious yawning to several regions involved in social cognition and emotional mirroring. These regions include the ventromedial prefrontal cortex, superior temporal sulcus, amygala, and insula. The same neural network also plays a central role in mother-infant bonding.
Yawning begins even before birth. Human fetuses have been observed yawning as early as the eleventh week of gestation, making it one of the earliest coordinated behaviors to emerge during development.
These prenatal yawns appear to reflect healthy development of both the brainstem and peripheral neuromuscular system. Researchers also believe they are linked to an ultradian rhythm of vigilance. In addition, yawning helps exercise the muscles and neural circuits that later become essential for breathing and swallowing.
Yawning frequency follows a U-shaped developmental pattern. Premature infants yawn more often than full-term babies, suggesting that the reflex gradually becomes refined and integrated into a broader behavioral repertoire over time.
But researchers had largely attributed these prenatal yawns to endogenous body programming, a kind of automatic neural housekeeping distinct from the socially contagious reflex that strikes children and adults. Notably, children are immune to contagious yawning until around five years of age, suggesting the social dimension of yawning develops gradually after birth. Whether a mother’s yawning had any impact on the fetus remained entirely unknown.
Pregnancy is a time when mothers and their fetuses are inextricably linked not just physiologically, but perhaps behaviorally, says Giulia D’Adamo, a neuroscientist and psychologist at the University of Parma in Italy. “During pregnancy, everything is groundwork for what is going to happen next.”
To test whether fetuses catch yawns from their mothers, the researchers recruited 38 pregnant women between 28 and 32 weeks into healthy, uncomplicated pregnancies. In a quiet room, the participants watched three types of videos: a yawning video, a mouth-movement control video, and a still-face control video.
A camera monitored each motherโs face, while a 2D ultrasound provided a real-time view of the fetusโs nose and lips. Three expert coders, who were unaware of which video the mother was watching, reviewed and verified the yawns.
The researchers also used DeepLabCut, an AI-based motion-tracking tool, to quantify subtle lip and nose movements with precision. They then trained a neural network to distinguish genuine yawns from other mouth openings.
Roughly 64 percent of the mothers yawned during the contagion condition. This rate is higher than the 40 to 60 percent typically reported in the general population. The finding aligns with prior research suggesting that pregnant women may be especially susceptible to yawn contagion. Hormonal and neurobiological changes may heighten sensitivity to social and emotional stimuli during pregnancy.
Just over half of the fetuses responded to their mothers by yawning about a minute and a half later. This response occurred well within the roughly five-minute window in which humans are susceptible to catching a yawn. Fetal yawns were far more likely to follow maternal yawns than to occur spontaneously.
True mother-fetus pairs also showed stronger temporal coherence than recombined dyads. These recombined pairs were artificially matched across different sessions. The result rules out coincidence and points to a genuine dyadic signal.
The channel through which the yawn travels remains unclear. It’s possible that the physical movement of a yawn puts pressure on the uterus in ways that signal to the fetus that it should yawn too, D’Adamo says. Hormonal messengers oxytocin, which plays a central role in maternal bonding and is already elevated during pregnancy, is one candidate could also prompt a fetal yawn. Future studies examining women at various stages of pregnancy, and directly measuring hormonal changes during maternal yawning, could help uncover the mechanism.
These findings challenge the view that fetal behavior is purely reflexive or entirely self-contained, the authors write. Instead, they suggest that a fetusโs behavior is already embedded within a shared biological context with its mother.
The study also indicates that examining maternal behavior and its effects on fetal activity may clarify the earliest foundations of co-regulation and embodied development. These early processes may later support motor and social competencies after birth.
But for now, it’s unclear whether fetuses catching yawns serves any direct adaptive purpose, or if those early echoes simply reflect the deep physiological entanglement of mother and child. The real social context, D’Adamo says, happens after birth.
Reference:
Giulia D’Adamo et al, Prenatal behavioral contagion through maternal yawning and fetal resonance, Current Biology (2026). DOI: 10.1016/j.cub.2026.04.025
Journal information: Current Biology
